Array Declaration-Error in Java

Question

Why

int arr[][]=new int[5][];

declaration is perfectly fine but

int arr[][]=new int[][5]    

generates compile time error ?
Please do help me. I am not able to understand why is that so?

Answer 1

int arr[][] (which is more typically written as int[][] arr) is an array, each element of which is in turn a reference to an array.

new int[][5] would mean "create an array of unknown length, each element of which is a reference to an array, each of length 5". Obviously, that doesn't make sense.

On the other hand, new int[5][] means "create a length-5 array, each element of which is a null reference to an array".